The present invention relates to the field of study of vegetation, more particularly plants, in the field of forestry and agriculture, and has for its object a device for non-destructive analysis of plants, as well as an analysis vehicle comprising such a device on board.
So as to optimize the exploitation of agricultural and forest services, it is essential to be able to determine the limit factors of the growth of the plants and to detect as soon as possible the appearance of undesirable factors.
Thus, so as to study and quantify the influence of deficiencies, hydric stresses and maladies of parasitic origin in vegetation, various types of analyses are at present known and generally carried out in a laboratory after removing specimens from the plants to be studied.
However, these extraneous analyses do not permit taking account of the environment of the plant in question, requiring complicated and fastidious removals and processing, permitting the study of only certain portions of a plant (for plants of large size) or of certain plants at the periphery of a field, which can lead to the destruction of the plant in question and do not give immediate on site results adapted to orient in place the ultimate analyses by the selection of certain plants or portions of plants, as a function of previous results.
The need for a non-destructive analysis, carried out remotely and performed on plants such as are present in their natural media (food supply, exposure to wind and sun, orientation and the like), has been apparent for a number of years.
Moreover, the principle of measuring by fluorescence is known, which consists in acquiring optically the image of the fluorescence of the vegetation, particularly the leaves, induced by a short luminous excitation, from a laser beam projected on these.
There already now exist several devices which permit carrying out measurements to extract information by the method of induced fluorescence of vegetation.
Thus, there is known for example:
from the document xe2x80x9cPlant Efficiency Analyzerxe2x80x9d of HANSATECH, the general principle of measuring by fluorescence of the plants, as well as the results which can be derived therefrom. Moreover, this document discloses an apparatus permitting measuring on a leaf the luminous emission produced after excitation by electroluminescent diodes, the measurement being carried out over a small surface by a photodiode;
from the document J. Plant Physiol., Vol. 148, pages 632 to 637, 1996, xe2x80x9cRemote Fluorescence Measurements of Vegetation Spectrally Resolved and by Multi-Colour Fluorescence Imagingxe2x80x9d, JONAS JOHANSSON et al., a device for remotely measuring by laser fluorescence and recovery of images produced by fluorescence at different wavelengths. In this document, the fluorescence is measured over all no matter what the region of interest in the image, by interposition of a spectrophotometer which sweeps the different wavelengths successively and a second path permits acquisition of two simultaneous images at two different frequencies.
from the document Aust. J. Plant Physiol., 1994, 22, pages 277 to 284, xe2x80x9cQuantitative Mapping of Leaf Photosynthesis using Chlorophyll Fluorescence Imagingxe2x80x9d, Bernard Genty et al., there is known a device for measuring by fluorescence the photosynthesis of a leaf, after removing it from its environment, by a measuring device in a laboratory, the system described not being adapted for overall on site measurement.
However, the known devices mentioned above do not give sufficient information to permit precise analysis and establishment of a diagnosis after a single measuring session, and none of these known devices is adapted to carry out, with the same device, an overall on site measurement and a measurement of a particular specimen.
Moreover, none of these devices permits entirely avoiding parasitic luminosity, nor parasitic influences generated by its control means.
Finally, none of these known devices provides a device of simple and easily transportable structure for on site measurements.
The invention particularly has for its object to overcome one or several of these drawbacks of the known devices mentioned above.
To this end, the invention has for its object a device for the non-destructive analysis of plants, and more generally of vegetation, by measurement of the fluorescence induced by laser excitation, comprising a unit for the emission of a calibrated excitation laser beam, a unit for measuring and taking images of the fluorescence emitted by the irradiated plant or plants and a digital processing unit, for storing and editing or visualizing the collective images, associated with a computer unit for the control and management of the operation of the device, which device is characterized in that the emission unit supplies at least two excitation laser wavelengths and in that the unit for measuring and collecting images comprises means to form, from a single beam of fluorescence emitted by the plant or plants simultaneously or successively, at least two secondary beams, each having its own wavelength and each constituting a fluorescent image in a matrix sensor, over all the surface of this latter (successive acquisition of images) or a portion of the surface of this latter, separately for each secondary beam (simultaneous acquisition of images).
The invention also has for its object a vehicle for the on site analysis of plants and, more particularly of vegetation, characterized in that it comprises at least one analysis device as mentioned above, mounted in a manner to be oriented and inclined on a telescoping beam.